Ive got a R reg P38 with an oldish single point conversion

MPG wise i get about 10mpg on local runs & up to 20mpg on fast roads etc

Some one reckoned (that good old mate of a mate said...) that new (multi point) conversions get about double that.

Any one know if multi point / newer systems get much better MPG, & if so how easy / pricey is it to upgrade?

Ne ideas?